. Very clear tracking and the booster RUD was like a supernova explosion. Incredibly beautiful
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SpaceX Starship - Integrated Flight Test #2 - Starbase TX - Including Post Launch Dissection
- Thread starter Grendal
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It doesn’t speculate the reason as Ship going of course. Generically as ‘ship performance data” which could mean any number of things
The engines shut down a few seconds before telemetry was lost. Combine that with the plume at 7:05 and LOX level readout and it seems to indicate a possible chain of events...
So, coupling the SpaceX report which suggests no FTS, Manley's hypothesis of fluid issues based on the deceleration and engine outs we see on the SpaceX telemetry graphics, the video depicting engine explosions and the burst at the bulkhead, what further guesses can we take?
The potential fuel-slosh/fluid hammer leading to engine outs would seem logical. Discussion on the NSF forums also suggest the deceleration caused an ullage collapse that starved the engines of fuel. I assume a Raptor ingesting gas, rather than fluid, and then suddenly being flooded with prop a moment later is good reason for blowing up...
Would the shock from either the fluid hammer, the ullage collapse, or the Raptor RUDs be such that it would cause tank rupture like that?
Or is it more likely the bending forces from the flip + Starship Raptor exhaust were too much for it and it "broke" there?
Other?
Nah. It had completed the flip and was flying back towards the launch site for a long time before the bulkhead gave way. There was a whole bunch of explosions back by the engines, and then the bulkhead gave way. I assume that it was some kind of pressure wave from those explosions that burst the bulkhead. I always think of the downcomer because that provides the link between the area of the explosions and the bulkhead. Perhaps it got shoved forward by one of the explosions, rupturing the bulkhead.
That's straight out of science fiction, having half a spaceship tumbling along while venting propellant with pieces flying off. It's not the science fiction we wanted, but it's still science fiction.
If the downcomer failed during the turn, it might take some time for the change in mixture to propagate to the engines?
Negative acceleration in pipe plus radial loads plus LOX slosh can't have been pleasant.
Ah, so you think possible a downcomer tube failure led to the engines exploding, whereas it appears that @JB47394 was suggesting that was where pressure waves propagated upwards causing the bulkhead to burst.
I suppose it could be both... if it broke somewhere inside the tank fluid flow to the engines would be compromised, and it still would be a conduit in to the tank for a pressure wave...
Could be both, if a CH4/LOX mix was fed into a preburner, there could be a heck of a traveling pressure wave.
Seems an event at the bottom would have the largest pressure at the bottom (presdure vs largest mass fluid flow) versus building while traveling up the tube, unless the change at the downcomer/ tank interface causes the issue?
If the reasons speculated here are the ones for Booster failure, then the trigger for all that are the forces due to rapid deceleration and rapid attitude change - whose root cause is the hot staging.
Given that Booster's mass is small fraction (may be 1/10th) of the Ship at MECO, hot staging will necessarily cause sudden deceleration of the Booster. There is no getting away from that. That to me means, SpaceX has a big problem in that they have not solved Staging yet.
Remember the hot staging that was successfully executed in the past by Russians, for them recovering the first stage was not on their agenda. So their experience will not help here.
So is there a possibility SpaceX will have to go to drawing board and come up with something different from hot staging? That will be a big setback.
Given that Booster's mass is small fraction (may be 1/10th) of the Ship at MECO, hot staging will necessarily cause sudden deceleration of the Booster. There is no getting away from that. That to me means, SpaceX has a big problem in that they have not solved Staging yet.
Remember the hot staging that was successfully executed in the past by Russians, for them recovering the first stage was not on their agenda. So their experience will not help here.
So is there a possibility SpaceX will have to go to drawing board and come up with something different from hot staging? That will be a big setback.
I can easily see that downcomer having a bad day. If the liquid oxygen smacked the bulkhead during the negative acceleration, it would really stress both downcomer and bulkhead (but the distance may have been too great within the tank). Then there's the fact that there are reinforcement rings all along the downcomer. That would provide additional stress as the liquid oxygen flowed past in the wrong direction.
Hmmm. Then you get the whole thing all over again as the engines light and turn the booster. What a mess. That would definitely smack the bottoms of the tanks.
Interestingly, there is no venting from the sides of the booster. Everything seems to be venting from the base until the bulkhead lets go.
I went through that exercise earlier and it seems that they can crank up the thrust on the booster so that they keep a small forward acceleration while Starship is separating. They may just have missed the amount of negative acceleration the booster would experience at staging. It seems like an obvious goof, which is odd.
An alternate approach is to have a sensor on the booster to watch for dropping forward acceleration and to throttle up engines in response. I don't know if the response time would work out (staging is pretty abrupt), but it's another thought. Perhaps the whole thing can be done on sensors, like someone balancing a bat on their hand.
Important distinction: Deceleration vs reduction in acceleration
While in proximity, booster effectively deals with the full stack mass plus the force of Ship's acceleration (exhaust impingement). That does not means that booster must decelerate. Increasing booster thrust at the start (then ramping down) and/or giving Ship a slower throttle ramp both address the situation.
That may not be so hard to accomplish. The closer booster gets to the ship, the more booster will be slowed by the exhaust. To ram it requires booster to either build a decent differential velocity and/or have a thrust level higher than ship (double maybe?).
Hot ring dwell time may be a factor, though it seems they can throttle engines pretty darn quickly.
I feel the parallels too, Falcon 1 flight 3 was dealing with an unlit second stage, so it was a bit of a different situation.
I was composing the same post, on every point. So I'm in complete agreement with you.
I wonder if Elon told the engineers to not worry too much about saving the booster, but to make absolutely sure that Starship gets away cleanly. That's the only reason I can imagine them not accounting for this effect. Regardless, I bet they learned a huge amount from their sensors on the booster.
Yeah, I can totally see them purposely choosing a thrust profile on the risky to booster low end side as they would never want to find that point with newer better hardware later in the program.
It's like a working and likely overbuilt product. You are disincentivized to reduce margin until failure.
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